Field of the Invention
This disclosure relates to an optical scanning apparatus configured to allow optical members such as a rotary polygonal mirror to be mounted in an internal space closed by a cover.
Description of the Related Art
In the related art, an image forming apparatus of an electrophotographic system is provided with an optical scanning apparatus configured to emit a light beam on the basis of image data. The optical scanning apparatus is provided with optical members such as a rotary polygonal mirror configured to deflect a light beam emitted from a light source so as to allow the light beam to scan on a photosensitive member, lenses configured to guide the light beam deflected by the rotary polygonal mirror onto the photosensitive member, and reflective mirrors.
With the scanning with the light beam emitted from the optical scanning apparatus, an electrostatic latent image on the basis of image data is formed on the photosensitive member provided in the image forming apparatus. The electrostatic latent image is developed with toner, and a toner image on the photosensitive member is transferred to a recording medium such as paper, whereby an image is formed on the recording medium.
The optical scanning apparatus is provided with an optical box, and a cover (lid) to be mounted on the optical box. The rotary polygonal mirror, the lens, and the mirror are installed in an internal space formed by the optical box and the cover.
Japanese Patent Laid-Open No. 2006-150687 discloses an optical scanning apparatus in which a cover is fixed to an optical box with a snap-fit mechanism. The snap-fit mechanism includes a cover-side engaging portion and a box-side engaging portion. With the engagement between the cover-side engaging portion and the box-side engaging portion, the cover is fixed to the optical box.
However, the optical scanning apparatus disclosed by Japanese Patent Laid-Open No. 2006-150687 may be subjected to the following problems at the time of assembly of the optical scanning apparatus or at the time of assembly of the cover after maintenance (cleaning of the rotary polygonal mirror, the lenses, and the mirror) of the optical scanning apparatus in a factory. In other words, there may be a case where the cover-side engaging portion which constitutes part of the snap-fit mechanism may abut against a side wall of the optical box or may enter the inside of the side wall of the optical box in the course of assembly of the cover to the optical box. At this time, if the pressure applied to the cover-side engaging portion is large, the cover-side engaging portion may be plastically deformed. If the cover-side engaging portion and the box-side engaging portion cannot be engaged as a result of plastic deformation of the cover-side engaging portion, the cover with the snap-fit mechanism cannot be fixed firmly to the optical box, and a gap is formed between the cover and the optical box. If dust enters from the gap, lowering of image quality may result.
In order to avoid such a problem, an operator is required to perform the assembly operation between the cover and the optical box carefully. However, there arises a problem of increase in assembly time required for a careful operation. In the case where the assembly operation of the cover and the optical box is performed an automatic machine, higher accuracy of an operation of the automatic machine is wanted, so that the design of the automatic machine may be complicated.